1. Field of the Invention
This invention relates to a carburetor with an auxiliary accelerator-pump system, and more particularly to a carburetor having an accelerator-pump system which can cope with fuel leakage into the intake passage due to an ambient temperature rise.
2. Description of the Prior Art
It is known that the operational characteristics of an internal combustion engine under cold weather can be improved by providing a vacuum-operated auxiliary diaphragm pump which operates only when the engine is cold, in addition to a mechanical accelerator pump which is adapted to supply additional fuel to the engine upon the sudden opening of the throttle valve.
With prior art diaphragm pumps of this type, the interior of the pump is separated by a spring-loaded diaphragm into a vacuum chamber (a vacuum is introduced therein from an intake passage in a carburetor) and a fuel chamber. The vacuum chamber is communicated by way of a temperature responsive valve, which is adapted to be closed at temperatures above a given level, with a vacuum take-off port in the intake passage, while the fuel chamber is communicated by way of a first check valve to a lower portion of a fuel reservoir or float bowl on one hand and on the other hand by way of a second check valve to a pump jet which opens into the intake passage.
When the ambient temperature is raised and hence the fuel pressure in the auxiliary accelerator-pump is increased, the fuel present in the fuel chamber or in a passage leading thereto tends to leak through the pump jet into the intake passage, thereby providing an excessively rich mixture charge and thus impairing the desired operation of the engine.